Assessment of americium retention in bone by measuring 241Am in the skull with a whole-body counter / 中国辐射卫生

Objective To assess the retention of 241Am in the whole-body bone of worker by measuring the retention of 241Am in the skull. Methods A whole-body counter with high-purity germanium detector was used to measure the 59.5 keV full-energy peak count of 241Am in the skull. The efficiency of the measurement was calibrated by the digital skull phantom combined with the geometric model of the detector. The retention of 241Am in the worker’s skull was calculated. Results The proportion of skull dry weight relative to the whole-body bone dry weight was used as the coefficient to calculate the 241Am deposition in the whole-body bone from the measured activity of skull 241Am. Conclusion With the retention of 241Am in the skull and the proportion of skull dry weight, the retention of 241Am in the whole-body bone of the worker was calculated to be about 806 Bq.

Radiation dose estimation and protective measure discussion of 241Am-Be neutron source logging / 中国辐射卫生

Objective To investigate the radiation dose to operators in the process of 241Am-Be neutron source logging, and discuss neutron source management and protective measures for operators in well logging. Methods Through on-site observation and measurement of 241Am-Be neutron source logging in a company, we obtained the surface γ dose rate and neutron dose rate of the neutron source, as well as the operating time and distance of various processes including source taking, transfer, and loading, calculated the radiation dose to operators in various processes, and analyzed the source and proportion of the personal effective dose to operators. Results The effective doses of neutron irradiation and γ irradiation were 94.17 μSv and 2.72 μSv, respectively, for the combined processes of source tank inspection, transfer, and detection; 36.66 μSv and 24.08 μSv, respectively, for source loading and unloading; and 130.83 μSv and 26.80 μSv, respectively, for the whole neutron source logging process. The total annual effective dose of neutron source logging was 15.78 mSv, as estimated by logging 100 times per year. Conclusion In the process of 241Am-Be neutron source logging in the company, the effective dose to operators mainly arises from neutron irradiation. Therefore, it is necessary to strengthen neutron source management and take effective protective measures against neutron radiation.

Exploration of ²⁴¹Am measurement in fecal samples / 中国辐射卫生

@#<b>Objective</b> To preliminarily study and establish a method for measurement of the transuranic nuclide ²⁴¹Am in fecal samples, and to provide technical support for internal radiation monitoring of staff. <b>Methods</b> Fecal samples were collected with a self-made stool sampler and treated with a self-made carbonization and ashing furnace. DGA resin was used to separate and purify ²⁴¹Am from fecal samples. With ²⁴³Am as the tracer, the orthogonal method was used for condition optimization. <b>Results</b> The optimum conditions for separation and purification were: the acidity of HNO₃ added into the column, 6 mol/L; column flow rate, 0.6 mL/min; and the volume of analytical solution,12 mL. The method based on inductively coupled plasma mass spectrometry showed a detection limit of 9.79×10⁻⁴ Bq for ²⁴¹Am in fecal samples, which was satisfactory and feasible. <b>Conclusion</b> This method fills the vacancy of ²⁴¹Am measurement in fecal samples to some extent, which is of practical significance for internal radiation monitoring and protection for analysts.

Study on the radiation device of 241Am-Be neutron source and its dosimetric properties / 中国辐射卫生

Objective To design and build a set of experimental equipment for neutron radiation irradiation by using the 241Am-Be neutron source. Methods In the preliminary work, the spatial distribution data of the neutron energy spectrum and the gamma energy spectrum inside and outside the device were simulated by Monte Carlo method, and the changes of radiation fluence rate with spatial distribution was studied. The model of the 241Am-Be neutron device was established, and the neutron transport process in the irradiation field was studied using the method of shadow cone, inverse square law and other data analysis methods. Results Based on the simulation results, the normalized effective does of fast neutron fluence at the measurement point is about 72.9 pSv/n, and the one of photon fluence is about 3.04 pSv/γ. The ratio of effective dose of photon fluence to neuteon is about 4.17%. Conclusion Using Monte Carlo method, a standard model of 241Am-Be neutron source was constructed, the shadow cone design was optimized, and the feasibility of using the shadow cone conversion method to establish a standard neutron source radiation device was discussed.